EP0386638B2 - Use of selected lower carboxylic-acid ester oils in drilling fluids - Google Patents

Abstract

The invention describes the use of esters, which are fluid at room temperature and have flashpoints above 80 DEG C, selected from C1-15 monocarboxylic acids and/or mono or multifunctional alcohols as the oil phase or a component thereof in invert drilling muds which are suitable for the environmentally favourable extraction of petroleum or natural gas deposits and, in a closed oil phase, contain a dispersed aqueous phase together with emulsifiers, fillers, fluid loss additives and, if desired, other customary additives. In a further embodiment the invention relates to invert drilling muds of the aforementioned kind in which the oil phase contains esters of C1-15 monocarboxylic acids with mono and/or multifunctional alcohols mixed, if desired, with other components from the class of ecologically acceptable compounds.

Description

The invention describes new drilling fluids based on ester oils and based thereon Invert drilling muds, which are characterized by high ecological compatibility with good stability and Characterize usage properties. An important area of application for the new drilling fluid systems is offshore drilling for the development of oil and / or natural gas deposits, the invention in particular here aims to provide technically usable drilling fluids with high ecological compatibility To make available. The use of the new drilling fluid systems is particularly important in the marine area, but is not limited to this. The new flushing systems can also be used for general purposes find land-based drilling, for example in geothermal drilling, in water drilling, in the Execution of geoscientific drilling and drilling in the mining area. Basically here, too, that the ecotoxic Problem area is substantially simplified.

Oil-based drilling fluids are generally used as so-called invert emulsion muds, which consist of a three-phase system: oil, water and finely divided solids. It is about Preparations of the type of W / O emulsions, i.e. H. the aqueous phase is heterogeneously finely dispersed in the closed Oil phase distributed. To stabilize the overall system and to set the desired usage properties a plurality of additives are provided, in particular emulsifiers or Emulsifier systems, weighting agents, fluid loss additives, alkali reserves, viscosity regulators and the like. For details, reference is made, for example, to the publication P. A. Boyd et al. "New Base Oil Used in Low-Toxicity Oil Muds "Journal of Petroleum Technology, 1985, 137-142 and R. B. Bennett" New Drilling Fluid Technology - Mineral Oil Mud "Journal of Petroleum Technology, 1984, 975 to 981 and those therein literature cited.

The relevant technology has for some time been of importance in the reduction of ester-based oil phases of the problems caused by such oil rinses. This is how the US patents describe 4,374,737 and 4,481,121 oil-based drilling fluids, in which nonpolluting oils are to be used. Aromatic-free mineral oil fractions and vegetable oils are considered side by side and equivalent as nonpolluting oils of the type peanut oil, soybean oil, linseed oil, corn oil, refels oil or oils of animal origin as called whale oil. The ester oils mentioned here are all vegetable and animal Originated from triglycerides of natural fatty acids, which are known to have a high environmental impact and towards hydrocarbon fractions - even if they are free of aromatics - for ecological reasons have clear superiority.

Interestingly, however, no example of the above-mentioned US patents describes the use such natural ester oils in invert drilling fluids of the type concerned here. Mineral oil fractions are used throughout used as a closed oil phase. Oils of vegetable and / or animal origin come from not considered for practical reasons. The rheological properties of such oil phases are for the broad in practice the required temperature range from 0 to 5 ° C on the one hand and up to 250 ° C and above on the other not get under control.

In the mid-1980s, the affected industrial circles also over the possible use of decyl and tridecylacetate esters as a replacement for mineral oils for Invert drilling fluid discussed. However, it was pointed out that such esters could only be used in drilling fluids if the pH value the mean does not exceed 10 in order to avoid possible hydrolysis of the esters.

In practice, ester oils of the type concerned do not behave in the same way as those previously used Mineral oil fractions based on pure hydrocarbons. In practice, ester oils are also subject to and especially in W / O invert drilling muds of a partial hydrolysis. As a result, free carboxylic acids educated. The older applications P 38 42 659.5 and P 38 42 703.6 (D 8523 "use selected Describe ester oils in drilling fluids (I) "and D 8524" Use of selected ester oils in drilling fluids (II) ") the problems triggered by this and give suggestions for their solution.

The subject of these earlier applications is the use of ester oils based on selected ones Monocarboxylic acids or monocarboxylic acid mixtures and monofunctional alcohols with at least 2, preferably with at least 4 carbon atoms. The older applications describe that with the esters or Ester mixtures of monofunctional reactants are not only satisfactory in the fresh drilling fluid rheological properties can be set, but that it also succeeds, with joint use selected known alkali reserves to work in the drilling fluid and in this way undesirable corrosion withhold. The addition of lime (calcium hydroxide or lime) and / or the alkali reserve Co-use of zinc oxide or comparable zinc compounds provided. However, there is an additional one Restriction expedient. Should the undesired thickening of the oil-based Invert flushing system can be prevented, so is the amount of alkalizing additive and in particular limit the amount of lime. The maximum proposed amount is according to the disclosure of the above older registrations are scheduled for about 2 lb / bbl oil rinse.

The teaching of the present invention wants to avoid the last-mentioned problem in that a class of ester oils is used in drilling fluids of the type mentioned, which always occurs in the limited hydrolysis of the ester forms unproblematic carboxylic acids or carboxylic acid salts. The technical Realization of this idea lies in the selection of ester oils based on lower carboxylic acids Decrease 1 to 5 carbon atoms. Corresponding esters of acetic acid can be of particular importance here. The acetate salts formed in the partial hydrolysis of the ester oil have no emulsifier property that could substantially disrupt the W / O system.

Accordingly, the invention relates in a first embodiment to the use of esters of C _1-5 monocarboxylic acids and mono- and / or polyfunctional alcohols as oil phase or constituent of the oil phase of invert drilling muds which are flowable at room temperature and have flash points above 80 ° C. are suitable for environmentally friendly development of oil or natural gas deposits and in a closed oil phase a disperse aqueous phase together with emulsifiers, weighting agents, fluid loss additives lime as alkali reserve, the amount of lime to be used being 1 to 2 lb / bbl (lime / Drilling fluid) is limited and, if desired, contain other customary additives.

In a further embodiment, the invention relates to invert drilling fluids which are suitable for the stated purpose and which contain a disperse aqueous phase together with the additives mentioned in a closed oil phase and which are characterized in that the oil phase consists at least partly of the esters of C _1-5 monocarboxylic acids with 1- and / or polyfunctional alcohols.

Monocarboxylic acid esters of the type concerned according to the invention can be controlled via the selection of the alcohol components used for the esterification in their substance properties so that they can be used for the use determined according to the invention. Corresponding esters or ester mixtures which are flowable and pumpable even in the temperature range from 0 to 5 ° C. are preferably used. It is further preferred to use C _1-5 monocarboxylic acid esters or their mixtures with ecologically compatible components from the class of so-called nonpolluting oils which have a Brookfield (RVT) viscosity not above 50 mPas in the temperature range from 0 to 5 ° C. and preferably do not have above 40 mPas. The stated viscosity value of the oil phase is preferably at most about 30 mpas.

The C _1-5 carboxylic acid esters used in the drilling mud of the invention expediently have solidification values (pour point and pour point) below 0 ° C., preferably below -5 ° C. and in particular below -10 ° C. At the same time, particularly for safety reasons, the flash points of these esters should be chosen as high as possible, so that preferred limit values for the flash point are around 90 ° C. and preferably above 100 ° C.

The esters of lower carboxylic acids suitable according to the invention can be divided into two subclasses. In a first class, the lower monocarboxylic acids are more monofunctional as reaction products Alcohols before. In this case, the C number of the alcohol is at least 6, but is preferably higher, namely at least 8 to 10 carbon atoms. The second subclass of the ester oils affected here uses polyfunctional alcohols as an ester-forming component. Consider here in particular 2- to 4-valent alcohols, lower alcohols of this type with preferably 2 to 6 carbon atoms in particular are suitable. Typical examples of such polyhydric alcohols are glycol and / or propanediols. Either ethylene glycol and 1,2-propanediol and / or 1,3-propanediol are of particular importance to. Preferred in the case described here are the esters of polyhydric alcohols, fully esterified reaction products, although the invention - especially in the case of higher polyfunctional alcohols - does not is limited to this. In the latter case in particular, the use of partial esters can also be used higher polyfunctional alcohols with the lower carboxylic acids mentioned.

The most important esters for teaching the invention are derived from monocarboxylic acids having 2 to 4 carbon atoms from, the acetic acid already mentioned being of outstanding importance as an ester-forming component.

An important thought for the selection of the respective alcohols is based on the following additional considerations back: When the ester oil is used in practice, partial saponification of the ester is generally the case not be ruled out. In addition to the resulting free carboxylic acids or together with the alkali reserve The free alcohols are formed when the carboxylic acid salts form. Your selection should be made that even after partial hydrolysis, ecologically and toxicologically safe working conditions are ensured are, especially the area of inhalation toxicological considerations is taken into account. The alcohols used for ester formation are said to be particularly low in volatility have that in the free state under the working conditions to be expected in practice to none Lead harassment on the work platform. For the class of ester oils based on the invention selected very short-chain monocarboxylic acids, the need arises from the outset, comparatively long chain monofunctional alcohols to reduce the volatility of the Ester oil to come. The considerations discussed here are therefore particularly important in the cases in which ester oils of the type defined according to the invention are blended with other blend components, in particular other carboxylic acid esters are used. The invention puts it overall in the preferred Embodiment depends on the fact that even after a partial hydrolysis in use, the drilling fluids Ecologically and toxicologically - especially here under inhalation-toxicologically working conditions - harmless are.

Suitable alcohols, especially suitable monofunctional alcohols, can be of natural and / or synthetic origin. Straight-chain and / or branched-chain alcohols can be used. The chain length in the presently predominantly aliphatic saturated alcohol is preferably in the range from C _8-15 . However, 1- and / or polyolefinically unsaturated alcohols are also suitable, as can be obtained, for example, by selective reduction of naturally occurring unsaturated fatty acids or fatty acid mixtures. Such 1 - and / or polyolefinically unsaturated alcohols can then also achieve higher C numbers in the ester oils according to the invention and are, for example, up to about C ₂₄ .

Ester oils of the type mentioned here can form the closed oil phase of the W / O invert rinse as a whole form. On the other hand, technical action falls within the scope of the invention, in which the invention defined carboxylic acid esters only make up a mixture component of the oil phase. As further oil components are practically any previously known and / or previously described oil components of the affected here Suitable area of application. The following is a particularly suitable mixture component still received.

The ester oils provided according to the invention can generally be mixed homogeneously with the mixture components in any desired mixing ratios. Appropriately, within the scope of the action according to the invention, at least about 25% and in particular at least about a third of the oil phase are present in the form of the C _1-5 ester oils. In important embodiments of the invention, these ester oils form the major part of the oil phase.

Mixture components in the oil phase

Suitable oil components for blending with the monocarboxylic acid esters of the invention are those in US Pat Today's practice of drilling fluids used mineral oils and preferably essentially aromatics-free aliphatic and / or cycloaliphatic hydrocarbon fractions with the required flow properties. On the relevant state of the art in print and the commercial products on the market is referred.

However, particularly important mixture components are in the sense of the action according to the invention Environmentally compatible ester oils such as those in the older applications mentioned ... (D 8523 and D 8524) are described. The following are essential to complete the disclosure of the invention Characteristics of such esters or ester mixtures briefly summarized.

In a first embodiment, flowable and pumpable esters of monofunctional alcohols with 2 to 12, in particular with 6 to 12 C atoms and aliphatic saturated monocarboxylic acids with 12 to 16 C atoms or a mixture thereof with at most approximately in the temperature range from 0 to 5 ° C equal amounts of other monocarboxylic acids used as the oil phase. Preferred are ester oils which are at least about 60% by weight, based on the respective carboxylic acid mixture, of esters of aliphatic C _12-14 monocarboxylic acids and, if desired, the remainder to minor amounts of shorter-chain aliphatic and / or longer-chain, then in particular 1- and / or or polyolefinically unsaturated monocarboxylic acids. Esters are preferably used which have a Brookfield (RVT) viscosity in the temperature range from 0 to 5 ° C. in the range not above 50 mPas, preferably not above 40 mPas and in particular of at most approximately 30 mPas. The esters used in the drilling mud show solidification values (pour point and pour point) below - 10 ° C, preferably below - 15 ° C and in particular have flash points above 100 ° C, preferably above 150 ° C. The carboxylic acids present in the ester or ester mixture are straight-chain and / or branched and are of vegetable and / or synthetic origin. They can be derived from appropriate triglycerides such as coconut oil, palm kernel oil and / or babassu oil. The alcohol residues of the esters used are derived in particular from straight-chain and / or branched saturated alcohols with preferably 6 to 10 C atoms. These alcohol components can also be of vegetable and / or animal origin and have been obtained by reductive hydrogenation of corresponding carboxylic acid esters.

Another class of particularly suitable ester oils is derived from olefinically 1- and / or polyunsaturated monocarboxylic acids with 16 to 24 carbon atoms or their mixtures with minor amounts of other, in particular saturated monocarboxylic acids and monofunctional alcohols with preferably 6 to 12 carbon atoms. These ester oils are also flowable and pumpable in the temperature range from 0 to 5 ° C. Particularly suitable are esters of this type, which are derived from more than 70% by weight, preferably more than 80% by weight and in particular more than 90% by weight of olefinically unsaturated carboxylic acids in the range from C _16-24 .

Here, too, the solidification values (pour point and pour point) are below half - 10 ° C, preferably below - 15 ° C, while the flash points are above 100 ° C and preferably above 160 ° C. The one in the drilling mud esters used show a Brookfield (RVT) viscosity of in the temperature range from 0 to 5 ° C not more than 55 mPas, preferably not more than 45 mPas.

Two subclasses can be defined for ester oils of the type concerned here. In the first, the unsaturated C _16-24 monocarboxylic acid residues present in the ester are derived to no more than 35% by weight from bi- and poly-olefinically unsaturated acids, preferably at least about 60% by weight of the acid residues being simply olefinically unsaturated , In the second embodiment, more than 45% by weight, preferably more than 55% by weight, of the C _16-24 monocarboxylic acids present in the ester mixture are derived from 2-and / or poly-olefinically unsaturated acids. Saturated carboxylic acids in the range C _16/18 present in the ester mixture advantageously make up no more than about 20% by weight and in particular no more than about 10% by weight. Saturated carboxylic acid esters, however, are preferably in the range of lower C numbers for the acid residues. The present carboxylic acid residues can be of vegetable and / or animal origin. Herbal raw materials are, for example, palm oil, peanut oil, castor oil and in particular rape oil. Carboxylic acids of animal origin are, in particular, corresponding mixtures of fish oils such as herring oil.

Suitable mixture components are finally those in the parallel application ... (D8607 "Ester of carboxylic acids of medium chain length as a component of the oil phase in invert drilling muds ") Esters from monocarboxylic acids of synthetic and / or natural origin with 6 to 11 carbon atoms and 1- and / or polyfunctional alcohols, which preferably also flow and in the temperature range from 0 to 5 ° C. are pumpable. To complete the disclosure of the invention, reference is made to the aforementioned parallel application referenced, the content of which is hereby also made the subject of the present disclosure.

Other mixing components of the invert drilling fluid

All usual mixture components for conditioning and for practical purposes come into consideration here Use of the Invert drilling mud, as is the case today with mineral oils as a closed oil phase come into use. In addition to the disperse aqueous phase, emulsifiers, Weighting agents, fluid loss additives, viscosity formers and alkali reserves.

In a particularly important embodiment of the invention, use is also made of the Further development of such invert drilling fluids based on ester oil, which is the subject of the older application ... (D 8543 "Olephile basic amine compounds as an additive in invert drilling muds") by the applicant.

The teaching of this earlier application is based on the concept of invert drilling fluids based on Ester oils to use an additional additive that is suitable, the desired rheological data to keep the drilling fluid in the required range even when increasingly large quantities are in use free carboxylic acids are formed by partial ester hydrolysis. These released carboxylic acids Not only should they be intercepted in a harmless form, it should also be possible to intercept them free carboxylic acids, if desired, to valuable components with stabilizing or emulsifying Convert properties for the entire system. According to this teaching, the use of basic and amine compounds capable of salt formation with carboxylic acids, distinctly oleophilic in nature and at most limited water solubility as an additive in the oil phase. The oleophilic amine compounds can also be used at least partially as an alkali reserve of the invert drilling fluid, they can also be used in combination with conventional alkali reserves, especially together with lime become. Preferred is the use of oleophilic amine compounds, at least predominantly are free of aromatic components. In particular, olefinic may be considered unsaturated aliphatic, cycloaliphatic and / or heterocyclic oleophilic basic amine compounds, which contain one or more N groups capable of salt formation with carboxylic acids. The water solubility at room temperature this amine compound is in a preferred embodiment at most about 5% by weight and is expediently below 1% by weight.

Typical examples of such amine compounds are at least largely water-insoluble primary, secondary and / or tertiary amines, which are also alkoxylated to a limited extent and / or with in particular hydroxyl groups can be substituted. Further examples are corresponding aminoamides and / or nitrogen as a ring component containing heterocycles. Basic amine compounds, for example, are at least suitable a long-chain hydrocarbon radical with preferably 8 to 36 carbon atoms, in particular with 10 to 24 Have carbon atoms, which can also be 1 or more olefinically unsaturated. The oleophilic basic Amine compounds can be used in drilling fluids in amounts up to about 10 lb / bbl, preferably in amounts up to about 5 lb / bbl and especially in the range of about 0.1 to 2 lb / bbl.

It has been shown that the concomitant use of such oleophilic basic amine compounds thickened of the flushing system can effectively prevent, which is probably due to a fault in the W / O inverter system and are due to the formation of free carboxylic acids by ester hydrolysis.

In the context of the teaching according to the invention, esters of longer-chain carboxylic acids are used as mixture components also used in the hydrolytic cleavage to fatty acids or fatty acid salts with pronounced O / W emulsifying effect, then the measures are also in the inventive action the alkali reserve to be taken into account, which is detailed in the older applications mentioned at the beginning P 38 42 659.5 and P 38 42 703.6 are described for this problem area. In the case of such ester mixtures the following then applies:

In a preferred embodiment of the action according to the invention, care is taken in the oil rinse no significant amounts of strongly hydrophilic bases of inorganic and / or organic type to be used. In particular, the invention dispenses with the use of alkali hydroxides or strongly hydrophilic ones Amines of the diethanolamine and / or triethanolamine type. Lime is effective as Alkali reserve also used. It is advisable to use the maximum amount of lime with about 2 lb / bbl, it may be preferable to add lime to the drilling mud load work slightly below, e.g. in the range of about 1 to 1.8 lb / bbl (lime / drilling fluid) lie. In addition to or instead of the lime, other known alkali reserves can be used. called estates here in particular the less basic metal oxides of the zinc oxide type. Even during use such acid scavengers will, however, be careful not to use too large amounts to an undesirable premature aging of the drilling fluid - combined with an increase in viscosity and thus Deterioration of the rheological properties - to prevent. Because of the special feature discussed here of the action according to the invention is the formation of undesirable amounts of highly effective O / W emulsifiers prevented or at least so limited that the good rheological application values also in the thermal aging in operation is maintained for a sufficiently long time.

The following also applies:

Invert drilling muds of the type concerned here usually contain together with the closed Oil phase, the finely dispersed aqueous phase in amounts of about 5 to 45 wt .-% and preferably in Amounts from about 5 to 25% by weight. The range from about 10 to 25% by weight of disperse aqueous phase can be of particular importance.

The following rheological data apply to the rheology of preferred invert drilling fluids for the purposes of the invention: plastic viscosity (PV) in the range from approximately 10 to 60 mPas, preferably from approximately 15 to 40 mPas, yield point (YP) in the range from approximately 5 up to 40 lb / 100 ft ² , preferably from about 10 to 25 lb / 100 ft ² - each determined at 50 ° C. For the determination of these parameters, for the measurement methods used and for the otherwise usual composition of the invert drilling fluids described here, the details of the prior art apply, which were cited at the beginning and are described in detail, for example, in the manual "Manual Of Drilling Fluids Technology "from NL-Baroid, London, GB, there in particular under" Mud Testing - Tools and Techniques "and" Oil Mud Technology ", which is freely accessible to interested professionals. In summary, the following can be said here for the purpose of completing the disclosure of the invention:

Emulsifiers which can be used in practice are systems which form the required W / O emulsions are suitable. Selected oleophilic fatty acid salts, for example, are particularly suitable those based on amidoamine compounds. Examples of this are found in the previously cited US patent 4,374,737 and the literature cited therein. A particularly suitable type of emulsifier is that of Company NL Baroid product sold under the trade name "EZ-mul".

Emulsifiers of the type concerned here are commercially available as highly concentrated active ingredient preparations sold and can for example in amounts of about 2.5 to 5 wt .-%, especially in amounts of about 3 to 4 wt .-% - each based on ester oil phase - are used.

As a fluid loss additive and thus in particular for the formation of a dense covering of the drilling walls with a largely liquid-impermeable film, in particular hydrophobicized lignite used. Suitable amounts are, for example, in the range from about 15 to 20 lb / bbl or in the range from about 5 to 7 wt .-% - based on the ester oil phase.

In drilling fluids of the type concerned here, the viscosity former usually used is cationic modified finely divided bentonite, which is used in particular in amounts of about 8 to 10 lb / bbl or in the range from about 2 to 4% by weight, based on the ester oil phase, can be used. That in the relevant practice The usual weighting agent used to adjust the required pressure balance is barite, the additional quantities of which are adapted to the conditions to be expected in the borehole. For example it is possible, by adding barite, the specific weight of the drilling fluid to values in the range up to approx 2.5 and preferably increase in the range of about 1.3 to 1.6.

The disperse aqueous phase is loaded with soluble salts in invert drilling fluids of the type concerned here. Calcium chloride and / or potassium chloride are predominantly used here, the saturation of the aqueous phase at room temperature with the soluble salt is preferred.

The previously mentioned emulsifiers or emulsifier systems may also serve to improve oil wettability to improve the inorganic weighting materials. In addition to the aminoamides already mentioned alkylbenzenesulfonates and imidazoline compounds are to be mentioned as further examples. additional Information on the relevant prior art can be found in the following references: GB 2 158 437, EP 229 912 and DE 32 47 123.

Those based on the use of ester oils of the type described In addition to the advantages already described, drilling fluid also has a clear advantage improved lubricity. This is particularly important when drilling in, for example greater depths of the passage of the drill pipe and thus also the borehole deviations from the vertical exhibit. The rotating drill pipe easily comes into contact with the borehole wall and digs in operation in this one. Ester oils of the type used according to the invention as an oil phase have a significantly better one Lubricating effect than the mineral oils previously used. Here is another important advantage for that acting according to the invention.

Examples

In the following examples, invert drilling fluids are produced in a conventional manner using the following frame formulation: 230 ml Esteröl 26 ml water 6 g organophilic bentonite (Geltone II from NL Baroid) 12 g organophilic lignite (Duratone from NL Baroid) xg Lime (x = 1 or 2) 6 g W / O emulsifier (EZ-mul NT from NL Baroid) 346 g barite 9.2 g CaCl ₂ x 2 H ₂ O

In this recipe, approximately 1.35 g of lime correspond to the value of 2 lb / bbl.

After in a manner known per se from the components used, varying the ester oil phase A W / O invert drilling fluid has been put together, first on the unaged and then determine the viscosity values for the aged material as follows:

Measurement of viscosity at 50 ° C in a Fann 35 viscometer from NL Baroid. The plastic viscosity (PV), the yield point (YP) and the gel strength (lb / 100 ft ² ) are determined in a manner known per se after 10 seconds and 10 minutes.

The aging takes place through treatment in an autoclave - in the so-called roller oven - for the period of 16 hours at 125 ° C.

Isotridecylacetate with the following rheological parameters is used as ester oil: Viscosity at 20 ° C 5 mPas; Viscosity at 50 ° C 2.1 mPas; Pour point below - 10 ° C.

In Example 1 below, the amount of lime used in the frame formulation is 2 g, in the example 2 this amount of lime is reduced to 1 g

The key figures determined for the unaged and aged material are in the following tabular summaries:

example 1

unaged material aged material Plastic viscosity (PV) 31 33 Yield point (YP) 11 13 Gel strength (lb / 100 ft ² ) 10 sec. 6 7 10 min. 9 9

Example 2

unaged material aged material Plastic viscosity (PV) 24 25 Yield point (YP) 14 12 Gel strength (lb / 100 ft ² ) 10 sec. 5 5 10 min. 8th 7

The basic formulation of these examples 1 and 2 corresponds to the numerical value in the weight ratio of oil phase / water from 90/10. In further experiments, tests are carried out with a modification of the ester oil / water ratio to the value of 80/20.

In these examples 3 and 4 below, invert drilling fluids are produced using the ester oil based on isotridecylacetate using the following basic formulation: 210 ml Esteröl 48.2 g water 6 g organophilic bentonite (omnigel) 13 g organophilic lignite (Duratone from NL Baroid) 2 g lime 8 g W / O emulsifier (EZ-mul NT from NL Baroid) 270 g barite 20 g CaCl ₂ x 2 H ₂ O

As in Examples 1 and 2, first the unaged and then the aged material (16 hours at 125 ° C in a roller oven) the viscosity values determined (Example 3).

In a further test approach (Example 4), the stated basic formulation of Example 3, a strongly oleophilic amine in an amount of 2 g (commercial product "Araphen G2D" from the applicant - the reaction product of an epoxidized C _12/14 alpha-olefin and diethanolamine) is added , Then, as stated above, the viscosity parameters are determined again on the unaged and then on the aged material.

Example 3

unaged material aged material Plastic viscosity (PV) 34 36 Yield point (YP) 52 51 Cel strength (lb / 100 ft ² ) 10 sec. 25 23 10 min. 37 35

Example 4

unaged material aged material Plastic viscosity (PV) 31 34 Yield point (YP) 36 32 Gel strength (lb / 100 ft ² ) 10 sec. 14 13 10 min. 17 15

Example 5

The ester oil used is the ester mixture of acetic acid and a C _6-10 alcohol cut (commercial product "Lorol technically" from the applicant), produced by reducing the corresponding lead fatty acid cut of natural origin. The basic formulation of the ester rinse corresponds to the formulation given at the beginning for example 2).

The viscosity data and the aging are determined as indicated in the previous examples. The following viscosity values are determined. unaged material aged material Plastic viscosity (PV) 28 29 Yield point (YP) 17 20 Gel strength (lb / 100 ft ² ) 10 sec. 9 9 10 min. 24 14

Examples 6 to 8

In parallel approaches, three drilling fluids based on isotridecalacetate are used in accordance with the framework recipe prepared according to Examples 1 and 2 (oil phase / water as 90/10). As in the previous examples your rheological data are stored in the roller oven immediately after manufacture and after aging 125 ° C determined for a period of 16 hours.

This is done in a first rinse without adding lime (example 6), in a second rinse (Example 7) 2 g of lime are added, while in the parallel third rinse (Example 8) 2 g of lime together with 1 g of the strongly oleophilic amine "Araphen G2D".

The rheological data determined in each case are the following:

Example 6

unaged material aged material Plastic viscosity (PV) 28 30 Yield point (YP) 15 9 Gel strength (lb / 100 ft ² ) 10 sec. 9 7 10 min. 10 8th

Example 7

unaged material aged material Plastic viscosity (PV) 30 29 Yield point (YP) 13 17 Gel strength (lb / 100 ft ² ) 10 sec. 8th 8th 10 min. 10 12

Example 8

unaged material aged material Plastic viscosity (PV) 25 25 Yield point (YP) 12 8th Gel strength (lb / 100 ft ² ) 10 sec. 8th 7 10 min. 11 9

Examples 9 to 11

In another comparative test series, drilling fluids based on isotridecylacetate are used in the Framework formulation of Examples 6 to 8 compiled as follows: Example 9 addition of 1 g of lime; Example 10 Addition of 2 g of lime; Example 11 Addition of 2 g of lime + 1 g of "Araphen G2D".

However, aging with these rinses is now in the rolleroven at 125 ° C for 72 hours performed. The rheological data determined on the non-aged and aged material are the following:

Example 9

unaged material aged material Plastic viscosity (PV) 30 37 Yield point (YP) 15 16 Gel strength (lb / 100 ft ² ) 10 sec. 7 7 10 min. 11 10

Example 10

unaged material aged material Plastic viscosity (PV) 28 34 Yield point (YP) 16 13 Gel strength (lb / 100 ft ² ) 10 sec. 6 6 10 min. 10 10

Example 11

unaged material aged material Plastic viscosity (PV) 29 36 Yield point (YP) 11 14 Gel strength (lb / 100 ft ² ) 10 sec. 7 6 10 min. 10 10

Claims (21)

1. The use of esters of C_1-5 monocarboxylic acids and mono- and/or polyhydric alcohols, which flow at room temperature and have flash points above 80°C, as the oil phase or as part of the oil phase of invert drilling muds which are suitable for the ecologically safe development of oil and gas occurrences and which, in a continuous oil phase, contain a disperse aqueous phase together with emulsifiers, weighting agents, fluid loss additives, lime as alkali reserve - the quantity of lime to be used being limited to 1 to 2 lb/bbl (lime/drilling fluid) - and, if desired, other standard additives.
2. The use claimed in claim 1, characterized in that esters or ester mixtures which are flowable and pumpable even at temperatures of 0 to 5°C are used.
3. The use claimed in claims 1 and 2, characterized in that the oil phase is formed by C_1-5 monocarboxylic acid esters or mixtures thereof with ecologically safe components (non-polluting oils) which have a Brookfield (RVT) viscosity at 0 to 5°C of not more than 50 mPas, preferably not more than 40 mPas and at most about 30 mPas.
4. The use claimed in claims 1 to 3, characterized in that the esters of the C_1-5 carboxylic acids used in the drilling mud have solidification values (flow and pour point) below 0°C, preferably below -5°C and, more preferably, below -10°C for flash points of no lower than 90°C and preferably above 100°C.
5. The use claimed in claims 1 to 4, characterized in that C_1-5 carboxylic acid esters of monohydric alcohols containing at least 6 carbon atoms, preferably at least 8 carbon atoms and/or esters of these acids with 2- to 4-hydric alcohols preferably containing 2 to 6 carbon atoms are used.
6. The use claimed in claims 1 to 5, characterized in that esters of glycol and/or a propanediol are used as the esters of polyhydric alcohols.
7. The use claimed in claims 1 to 6, characterized in that esters of C_2-4 monocarboxylic acids, more especially acetic acid esters, are used.
8. The use claimed in claims 1 to 7, characterized in that ester-based mixture components which are ecologically and toxicologically safe, above all inhalation-toxicologically safe under working conditions, even after partial hydrolysis in practical application, are used for mixing with other ester oils.
9. The use claimed in claims 1 to 8, characterized in that esters of monohydric alcohols of natural and/or synthetic origin, which have a chain length in the range from C₈ to C₁₅ where predominantly aliphatically saturated alcohols are present or an even greater chain length, for example up to C₂₄, where mono- and/or polyolefinically unsaturated alcohols are present, are used.
10. The use claimed in claims 1 to 9, characterized in that ester oils of monohydric C_2-12 and preferably C_6-10 alcohols and mono- and/or polyolefinically unsaturated C_16-24 monocarboxylic acids which preferably have solidification values (flow and pour point) below -10°C and preferably below -15°C for flash points above 100°C are used as ester-based mixture components in the continuous oil phase.
11. The use claimed in claim 10, characterized in that olefinically unsaturated carboxylic acid esters of which more than 70% by weight, preferably more than 80% by weight and, in particular, more than 90% by weight are derived from olefinically unsaturated C_16-24 carboxylic acids and which have a Brookfield (RVT) viscosity of no more than 55 mPas and preferably no more than 45 mPas, more particularly at temperatures of 0 to 5°C, are used as a mixture component together with the lower carboxylic acid esters.
12. The use claimed in claims 10 and 11, characterized in that no more than 35% by weight of the esters of unsaturated monocarboxylic acids used as mixture components are derived from di- and polyolefinically unsaturated acids, of which at least about 60% by weight are monoolefinically unsaturated, and/or of which more than 45% by weight and preferably more than 55% by weight are derived from di- and/or polyolefinically unsaturated acids.
13. The use claimed in claims 1 to 9, characterized in that esters of aliphatically saturated monocarboxylic acids containing 6 to 16 carbon atoms esterified with mono- and/or polyhydric alcohols are used as mixture components.
14. The use claimed in claims 1 to 13, characterized in that the esters or ester mixtures are used in the invert drilling muds together with amino compounds of pronounced oleophilic character and at most limited solubility in water which are capable of forming salts with free carboxylic acids.
15. The use claimed in claims 1 to 14, characterized in that the esters are used in drilling fluids which, in the invert drilling mud, contain the finely disperse aqueous phase in quantities of from about 5 to 45% by weight and preferably in quantities of from about 5 to 25% by weight together with the continuous ester-based oil phase.
16. Invert drilling fluids which are suitable for the ecologically safe development of oil and gas occurrences and which, in a continuous oil phase, contain a disperse aqueous phase together with emulsifiers, weighting agents, fluid loss additives, lime as alkali reserve - the quantity of lime to be used being limited to 1 to lb/bbl (lime/drilling fluid) - and, if desired, other standard additives, characterized in that the oil phase contains esters of C_1-5 monocarboxylic acids with mono- and/or polyfunctional alcohols which flow at room temperature and have flash points above 80°C, if desired in admixture with other components from the class of ecologically safe compounds (non-polluting oils).
17. An invert drilling fluid as claimed in claim 16, characterized in that esters of C_2-4 monocarboxylic acids, particularly acetic acid esters, and monohydric alcohols containing at least 8 carbon atoms and/or corresponding esters with, in particular, lower 2- to 4-hydric alcohols are present in the oil phase.
18. An invert drilling fluid as claimed in claims 16 and 17, characterized in that the ester oils of the C_1-5 carboxylic acids make up at least about 25% by weight, preferably at least about one third and, more preferably, the predominant part of the oil phase.
19. An invert drilling fluid as claimed in claims 16 to 18, characterized in that it has a plastic viscosity (PV) in the range from about 10 to 60 mPas and a yield point (YP) in the range from about 5 to 40 lb/100 ft², as determined at 50°C.
20. An invert drilling fluid as claimed in claims 16 to 19, characterized in that its disperse water content makes up about 5 to 45% by weight and preferably about 10 to 25% by weight and, in particular, contains dissolved salts of the CaCl₂ and/or KCI type.
21. An invert drilling fluid as claimed in claims 16 to 20, characterized in that the oil phase of the invert mud has a Brookfield (RVT) viscosity at 0 to 5°C below 50 mPas and preferably of not more than 40 mPas.